The most succinct definition of the gospel is found in 1 Corinthians 15:1-4.

“Now I would remind you, brothers, of the gospel I preached to you, which you received, in which you stand, and by which you are being saved, if you hold fast to the word I preached to you—unless you believed in vain.  For I delivered to you as of first importance what I also received: that Christ died for our sins in accordance with the Scriptures, that he was buried, that he was raised on the third day in accordance with the Scriptures.”

Jeremiah Burroughs, a 17th Puritan preacher thoroughly expounds the gospel as follows:

“And now this mediation of Christ is, by the appointment of the Father, preached to the children of men, of whatever nation or rang, freely offering this unto sinners for atonement for them, requiring them to believe in Him and, upon believing, promising not only a discharge of all their former sings, but that they shall not enter into condemnation, that none of their sins or unworthiness shall ever hinder the peace of God with them, but that they shall, through Him be received into the number of sons.  They shall have the image of God renewed again in them, and they shall be kept by the Power of God unto salvation.  These souls and bodies shall be raised to the height and glory that such creatures are capable of.  They shall live forever, enjoying the presence of God and Christ in the fullness of all good.  This is the gospel of Christ.”

John Piper wrote a book called “God is the Gospel”.  In it, Piper makes the case that God Himself (as revealed in Jesus’s death and resurrection) is to be seen as the final and greatest gift of the gospel.  To this I say “Amen”.  In my view, the beauty of this perspective is that it raises our gaze from how we personally benefit from the gospel to the Gift-Giver Himself.

For my own part, I believe the Gospel can be summarized as follows:

The Gospel (the Good News) is that God, from the beginning of time, planned to put on flesh in the Son Jesus Christ who would die for sins and rise again to save out a people (formerly His enemies) who would glorify Him forever by being Christlike reflections of His wondrous attributes and glorious nature.

1 Timothy 3:16, Ephesians 1:4, John 12:20, Romans 8:7, 1 Corinthians 15:1-4; Hebrews 1:1-3; Colossians 1:15